This invention relates to pressure sensors in general and more particularly to a simplified mechanism for protecting pressure sensors from overload conditions. A pressure or pressure difference measuring apparatus having a central pickup body and a pressure sensor device protected against overload in a measuring chamber, the subchambers of which are connected by connecting canals to antechambers formed between separating diaphragms and the pickup body is described in U.S. Pat. No. 4,329,577. The apparatus also has supplementary diaphragms, resting against the pickup body with pre-tension and each arranged adjacent to a separating diaphragm, communicating therewith in a pressure-transmitting sense, and supplementary canals, running from the connecting canals to the supplementary diaphragms, each supplementary diaphragms being housed in a supplementary chamber filled with a filling liquid, the supplementary chambers being subdivided by the supplementary diaphagms into two subchambers, each of which is connected to a supplementary canal. The supplementary canals are arranged so that the supplementary canal leading to the adjacent side of the supplementary diaphragm and the supplementary canal leading to the nonadjacent side of the other supplementary diaphragm are connected to a connecting canal. Correspondingly, the other connecting canal is connected by two further supplementary canals to the respective other sides of the two supplementary diaphragms.
Another pressure or pressure-difference measuring apparatus, described in DE-A No. 26 57 933, contains an equalizing chamber, which is subdivided by an equalizing diaphragm, in the central pickup body. One subchamber of the equalizing chamber is connected to one antechamber of the apparatus and the other subchamber is connected to the other antechamber. The measuring chamber, housing the pressure sensor device of this apparatus, is connected by a connecting canal to the antechamber of a subchamber of the equalizing chamber and by a further connecting canal to the other antechamber or the other subchamber of the equalizing chamber. In this manner, a pressure or pressure-difference measuring apparatus is created which, due to the design of the equalizing diaphragm, forms a pressure equalizing path in the measuring chamber parallel to the pressure sensor device, whereby overloading of the pressure sensor device is prevented. The pressure sensor device in the known apparatus consists of a wall containing a semiconductor measuring diaphragm. Such pressure sensor devices are very sensitive to overload.
In another embodiment of a differential pressure measuring transducer, as described in DE-A No. 30 47 276, two canals are brought from the central pickup body into a separate structural unit, containing a pressure sensor device, arranged alongside the pickup body. This apparatus also utilizes a pressure sensor device consisting of a semiconductor sensor and protects against overloading by use of an equalizing chamber arranged parallel to the measuring chamber.
The known types of pressure or pressure-difference measuring apparatus have the disadvantage that their design is relatively complicated, since they require, in addition to a measuring chamber, a further equalizing chamber with a diaphragm, or supplementary chambers with supplementary diaphragms, which necessitates that either the pressure sensor unit is disposed in a supplemental structure provided next to the central pickup body, or that the connecting canal be brought out of the central pickup body and subsequently be brought back into the body.
It is an object of the present invention to provide an improved pressure or differential pressure measuring apparatus, having a central pickup body and a pressure sensor device protected against overload in a measuring chamber, which is distinguished by its relatively simple mechanical design.
Another object of the present invention is to provide an improved pressure or differential pressure measuring apparatus distinguished by its inexpensive production cost.
A further object of the present invention is to provide an improved pressure or differential pressure measuring apparatus distinguished over the prior art by its improved measuring characteristics.